To start with, this seems to be created by the people that made this movie for a convention:
https://www.youtube.com/watch?v=JIsOuO2qZBo&t=2s

I have part of this manga translated, I am sure it is legit though not canon, it follows the adventures of Magus and Frog if Marle is not in fact sent back in time. As you can prolly gather from the video, this book which is over 150 pages is mostly humorous, and in places quite stupid lol I know a bit of Japanese myself thanks to watching anime with subtitles, but I am no means fluent. So I guess we can prolly discuss page meanings and theories. I am going to post one or two pages and their rough translation and what's going on per post, this book is not scan friendly so photos will have to do. As a prerequisite, a good portion of the previous pages concern Frog, this Nu prince and his wee companion getting Frog's sword repaired in a less than...conventional way and thus they are now his companions facing the mage. (If you wanna hear how this is done I can explain but it's stupid lol) Basically all this page is sound effects, Frog yelling Demon lord, prepare yourself! And something about Magus versus and my bro didn't translate the rest but it can be inferred it is referring to Frog and his companions. And yes the nu is a prince come from another planet, run away from his responsibilities and travelling on earth lol